Biomass fuel stove

ABSTRACT

Disclosed is a biomass stove for burning biomass fuel using a combustion furnace. The stove includes a gravity feed fuel holding tank for feeding biomass fuel to the furnace. The combustion furnace includes a primary combustion furnace and a secondary combustion furnace surrounding the primary combustion furnace, as well as a water jacket surrounding the secondary combustion furnace and an air jacket further surrounding the water jacket. A fuel holding device may be in the form of a rotating furnace that includes a support surface with one or more curved vanes thereon for moving gravity fed fuel. An ash removal assembly includes an adjustable ash grate and a fixed ash grate below the furnace. Adjustment of the adjustable grate relative to the fixed grate moves openings into and out of alignment such that ash from burned biomass fuel is output to an ash pan.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application No. 62/185,160, filed Jun. 26, 2015, which is hereby incorporated by reference in its entirety.

BACKGROUND

Field

This disclosure is generally related to a biomass fuel or agricultural waste fired stove and, in particular, to a rotating furnace that provides feeding of biomass fuel to a combustion furnace.

Description of Related Art

Most farmers use firewood as fuel for processes that consume heat, such as to cure tobacco (or other materials) in barns. However, when using firewood, barn temperatures can be inconsistent, sometimes higher or sometimes lower than a desired temperature, and curing hours may vary. Supply of firewood can also be limited, and thus the cost of such fuel may be higher. Firewood also emits polluted gases (e.g., greenhouse gases, or GHG) when burned.

Other fuels that may be used for heating and/or curing, such as natural gas, liquefied petroleum gas, or diesel gas, tend to be expensive.

SUMMARY

It is an aspect of this disclosure to provide a biomass stove for burning biomass fuel using a combustion furnace. The stove includes a fuel holding tank for feeding biomass fuel to the combustion furnace, a rotating furnace positioned below the combustion furnace for receiving the biomass fuel from the fuel holding tank, and a motor. The rotating furnace includes a support surface configured for rotation by the motor, and the support surface is constructed to hold and position biomass fuel for burning in the combustion furnace.

Another aspect provides a biomass stove for burning biomass fuel using a combustion furnace. The stove includes a fuel holding tank for feeding biomass fuel to the combustion furnace, a fuel holding device for receiving the biomass fuel from the fuel holding tank and positioning biomass fuel for burning in the combustion furnace; and an ash removal assembly positioned below the combustion furnace for receiving ash from burned biomass fuel being discharged from the fuel holding device and distributing the received ash to an ash pan positioned below the ash removal assembly. The ash removal assembly includes an adjustable ash grate and a fixed ash grate. The fixed ash grate is positioned below the adjustable ash grate. Each grate has a plurality of openings therein. Adjustment of the adjustable ash grate relative to the fixed ash grate moves its openings into and out of alignment with openings on the fixed ash grate such that, upon substantial alignment of the openings, ash from burned biomass fuel is output to the ash pan.

Yet another aspect of this disclosure provides a biomass stove for burning biomass fuel using a combustion furnace assembly. The assembly includes a primary combustion furnace for burning biomass fuel and a secondary combustion furnace surrounding the primary combustion furnace. The secondary combustion furnace has an inner wall spaced from an outer wall of the primary combustion furnace. A water jacket surrounds the secondary combustion furnace and an air jacket further surrounds the water jacket. Also included is a fuel holding device for receiving the biomass fuel and positioning the biomass fuel for burning in the primary combustion furnace.

Other aspects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a biomass fuel stove in accordance with an embodiment of this disclosure.

FIG. 2 is a cross sectional view taken along line 2-2 in FIG. 1 of the biomass fuel stove.

FIG. 3 is an isometric view of a combustion furnace and air distribution assembly in the biomass fuel stove of FIG. 1 in accordance with an embodiment.

FIG. 4 is an exploded view of parts of the combustion furnace assembly of FIG. 3.

FIG. 5 is an isometric view of a rotating furnace and an ash removal assembly in the biomass fuel stove of FIG. 1 in accordance with an embodiment.

FIG. 6 is an exploded view of parts of the assembly of FIG. 5.

FIG. 7 illustrates parts of a drive and shaft assembly of the rotating furnace and ash removal assembly of FIG. 5 in accordance with an embodiment.

FIG. 8 is a side view of a biomass fuel tank assembly in the biomass fuel stove of FIG. 1 in accordance with an embodiment.

FIG. 9 is an exploded view of parts of the biomass fuel tank assembly of FIG. 8.

FIG. 10 is an exploded view of parts of a flue gas pipe assembly in the biomass fuel stove of FIG. 1 in accordance with an embodiment.

FIGS. 11-13 illustrate positions of a damper that may be used with a fan that is part of the biomass fuel stove.

FIG. 14 shows charts of results of fuel consumption between firewood versus rice husk in curing FCV tobacco gathered during a test run using the biomass fuel stove as described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

This disclosure is generally related to a multiple biomass fuel, or agricultural waste, gravity fed fired stove 100. Features and parts of the stove are illustrated in the accompanying drawings. One of ordinary skill in the art should understand that the associated parts of the stove need not be limited merely to those shown in the Figures, but, rather, understand that additional devices, systems, valves, sensors, and the like may be included in or with the stove 100.

The multi-biomass fuel stove 100 is illustrated in FIGS. 1 and 2. The multi-biomass fuel stove 100 may be used for a number of applications, including, but not limited to, as a source for heating and curing tobacco in one or more barns (or similar enclosed space(s)) (see FIG. 12), also referred to as a curing barn herein. The biomass fuel stove 100 includes a combustion furnace assembly 102 and air distribution assembly 104, a rotating furnace, an ash removal assembly 106 with a drive and shaft assembly 108, a biomass fuel tank assembly 110, and a flue gas pipe assembly 112. A structure and frame assembly 20 may be provided to support the weight of the parts forming the entire stove assembly and fuel. As generally understood, biomass fuel is supplied into a top portion of the biomass fuel tank assembly 110 for gravity feeding the biomass fuel and with the use of curved vane, biomass fuel moves towards the center of the furnace for burning by the combustion furnace assembly 102.

“Biomass fuel” is defined herein refers to biological material derived from living or recently living organisms. Biomass fuel may be animal or vegetable derived material, and may include agricultural waste. Examples of biomass fuel that may be utilized in the disclosed stove 100 include, but are not limited to: almond shells, cocoa shells, coconut shells, coco peat, coffee bean shells, peanut shells, pistachio shells, soybean pods, sunflower seed shells, walnut shells, pellets, rice husks, corn husks, and corn cobs.

FIG. 3 illustrates the combustion furnace assembly 102 and air distribution assembly 104 in greater detail. The stove 100 includes a primary combustion furnace 6 as well as a secondary combustion furnace 7 surrounding the primary combustion furnace 6 that serves as an outer combustion cylinder (see also FIG. 2). Biomass fuel is gravity fed in a generally vertical direction from a surrounding biomass fuel tank assembly 110 towards and onto a fuel holding device (e.g., rotating furnace 26 (described later)) for burning by at least the primary combustion furnace 6. Generally, the wall of the primary combustion furnace 6 is cylindrical in shape and positioned in the center of the stove 100. This is the main combustion furnace for the stove and where a majority of flame is generated while firing biomass fuel. The biomass fuel at the base of primary combustion furnace 6 is lit via adding a flame or fire from its top (e.g., via door 4).

The primary combustion furnace 6 has a diameter D (see FIG. 3) in accordance with an embodiment. In an embodiment, the diameter D is approximately 8 inches. In an embodiment, the diameter D is within a range of approximately 6 inches to approximately 10 inches. Of course, it should be understood that such dimensions are exemplary only and not intended to be limiting with regards to this disclosure. For example, the furnace may not be circular or round and instead may include other dimensions such as a length and/or a width.

As seen in FIG. 4, the primary combustion furnace 6 may have air holes 23 at its bottom portion. The air holes 23 may be positioned around a bottom circumference of the cylinder, for example. The air holes 23 assist in allowing air to flow through the furnace such that the biomass burns and is heated effectively.

In one embodiment, the cylinder of the primary combustion furnace 6 is positioned to extend lower than the wall of the secondary combustion furnace to allow better combustion of biomass fuel. This is illustrated in FIG. 2, for example.

Generally, the secondary combustion furnace is cylindrical in shape and positioned around the primary combustion furnace 6, as shown in FIG. 2, for example. In one embodiment, the cylinder wall of the secondary combustion furnace 7 is positioned above a bottom of the primary combustion furnace 6 to allow better combustion of biomass fuel.

Surrounding the secondary combustion furnace 7 are a water jacket 9A and an air jacket 9B, respectively. The water jacket 9A and air jacket 9B are in the form of cylinders around the secondary combustion furnace 7. One function of the water jacket 9A is to act as an initial insulating layer to limit conductive heat transfer from the heat generated by the burning fuel in primary combustion furnace 6 and the secondary combustion furnace 7 to an outer fuel supply tank 110. Heat is transferred from the furnaces 6 and 7 to water in the water jacket 9A. The air jacket 9B functions as another layer of insulation for limiting heat transferred to the fuel supply in the tank assembly 110, further lowering down a temperature of the transferred heat to the fuel in the surrounding fuel tank of the fuel tank assembly 110. Heat is transferred from the heated water in the water jacket 9A to air in the air jacket cylinder 9B.

The secondary combustion furnace 7, water jacket 9A, and air jacket 9B are assembled such that adjacent walls are shared. More specifically, as shown in FIGS. 2 and 4, the combustion furnace assembly 102 may include three cylinders—an inner cylinder 7A, a middle cylinder 7B, and an outer cylinder 7C—that are assembled together, and mounted to encase or enclose the cylinder of the primary combustion furnace 6. Top and bottom covers 7D and 7E may be welded to the top and bottom portions of the cylinders 7A-7C to secure the cylinders together as one piece (and to cover the ends of both the water and air jackets). The inner cylinder 7A is spaced from the cylindrical wall of the primary combustion furnace 6 and forms an outer wall of the secondary combustion furnace 7. That is, the secondary combustion furnace 7 is formed between an outside wall (outside relative to a center line extending through a center of the furnace) of the primary combustion furnace 6, and an inside wall of the inner cylinder 7A. The middle cylinder 7B is positioned in-between inner and outer cylinders 7A and 7C to separate water and air and to form the water and air jackets 9A and 9B. That is, an outside wall of the inner cylinder 7A and an inside wall of the middle cylinder 7B forms a furnace of the water jacket 9A for containing water to cool down transferred heat from the primary combustion cylinder 6 therebetween. The middle and outer cylinders 7B and 7C form the air jacket 9B. An outside wall of the middle cylinder 7B and an inside wall of the outer cylinder 7C form a furnace for containing air to cool down transferred heat from the water jacket 9A.

The secondary combustion furnace 7 (or inner cylinder 7A) has a diameter D2 (see FIG. 3) in accordance with an embodiment. In an embodiment, the diameter D2 is within a range of approximately 8 inches to approximately 9 inches. The middle cylinder 7B has a diameter D3. In an embodiment, the diameter D3 is within a range of approximately 12 inches to approximately 13 inches. The outer cylinder 7C has a diameter D4. In an embodiment, the diameter D4 is within a range of approximately 15 inches to approximately 18 inches. Of course, it should be understood that such dimensions are exemplary only and not intended to be limiting with regards to this disclosure. That is, the secondary combustion furnace 7 may instead include dimensions such as a length and/or a width and may not be circular or round in shape.

The water jacket 9A is connected to a water inlet tank 21 via a fresh water supply pipe 24, such that fresh water may pass to the water jacket 9A. As shown in FIG. 3, for example, the supply pipe 24 may run parallel to the air distribution pipe 8 from the water inlet tank 21 and then downwardly relative to the combustion furnaces to provide an inlet of water near the bottom of the water jacket 9A. However, the placement and configuration of the water input and its piping is not limited to the illustrated embodiment. In an embodiment, the pipe 24 may be located around the water jacket 9A. The water may be input approximately 2 to 4 inches from the top of the water jacket 9A, for example. The water jacket 9A produces and releases hot water (e.g., boiling, or near boiling, water, and steam) to a water outlet pipe 11. Water inside the water jacket 9A absorbs heat transferred from the primary combustion cylinder 6 and the secondary combustion furnace 7. In accordance with an embodiment, the water jacket 9A generates hot water with a temperature below 100 degrees Celsius. In accordance with one embodiment, the maximum temperature of the water generated by the water jacket is approximately 100 degrees Celsius.

The heat exchange to the water in the water jacket 9A as a result of the heat generated from fuel that is burning in in the primary combustion furnace 6 results in insulation before heat is transferred to the air in the air jacket 9B, thereby reducing heat transfer to the air in the air jacket cylinder 9B. As explained further below, the fuel tank surrounds the combustion furnace assembly 102, and fuel is held between walls of the outer cylinder 7C and the fuel tank. Accordingly, reducing heat transfer to the air in the air jacket 9B thus limits transfer of heat (via conduction) from the combustion furnaces to the biomass fuel in the fuel tank, protecting the fuel from carbonizing and generating smoke while inside the biomass fuel tank.

Besides functioning as an insulating layer, the water jacket 9B of secondary combustion furnace 7 also produces hot water (e.g., like a hot water boiler) for output. Hot water generated by water jacket 7 may be used for other heating applications and devices, such as in radiators, for hot showers, for heating applications to warm a home, and many others.

In the biomass stove 100, a correct combination of fuel and air ratio is critical for combustion efficiency. As shown in FIG. 3, the air distribution assembly 104 has an air distribution pipe 8 with an air manifold connected to a fan 10. The air manifold is used as support for the furnace assembly (flame) which sits on top of the fuel tank (described later). With this design, the primary and secondary combustion furnaces 6 and 7, including fan 10, may be detached from the machine, e.g., for maintenance. An optional damper (shown in FIGS. 11-13) may be provided to control intake air volume to match with incoming fuel at the combustion furnace to meet a desired fuel and air ratio. Air to the furnace (flame) may be introduced and controlled via the damper. For example, the damper may be a manually controlled damper that is closed (100% closed, as shown in FIG. 11), partially open (e.g., 50% open, as shown in FIG. 12), or fully open (100% open, as shown in FIG. 13), or provided at any number of positions therebetween (e.g., ¼ open, ¾ open, etc.) to control or limit air into the blower of the fan 10.

The air jacket 9B is connected to the fan 10 of the air distribution assembly 104 via the pipe 8. The fan 10 moves fresh (atmospheric) air through the air distribution pipe 8 through the air jacket 9B towards outlets provided in the form of nozzles 25. As shown in FIG. 4, for example, a bottom of the secondary combustion furnace 7 has multiple air nozzles 25 (in this illustrative case, there are four) that extend therefrom and form outlets for outputting the preheated air. The air nozzles 25 may be in the form of tubes, for example, having an inlet end and an outlet end. The bottom cover 7E includes a number of holes or openings such that inlet ends of the multiple air nozzles 25 may be connected thereto. The inlet ends of the air nozzles are connected to the bottom cover 7E such that air from the air jacket 9B (i.e., between middle and outer walls 7B and 7C) is output and forced, e.g., via fan 10, through the outlet ends of the air nozzles 25. The outlet ends of each of the nozzles 25 are positioned such that the preheated air from the air jacket 9B is aimed towards or at a center of the combustion furnace assembly 102.

Heat absorbed from the water jacket 9A preheats the air in the air jacket 9B before supplying to the air to the combustion furnaces 6 and 7 to combust biomass fuel. By supplying heated air from the air jacket 9B towards the primary and secondary combustion furnaces 6 and 7 and onto the biomass fuel that is positioned for firing (i.e., onto biomass fuel that is positioned on a middle of a rotating furnace 26), combustion of the biomass fuel is aided. Supplying preheated air to the primary combustion furnace 6 increases combustion efficiency and consumes less fuel. By directing the air towards the center, the system further aids in minimizing O2 content.

The secondary combustion furnace 7 and successive water and air jackets 9A and 9B not only produce hot water and generate preheated air, but also reduces or lowers temperatures as a result of conduction so that a temperature of the fuel in the tank maintains low temperature to prevent carbonization of biomass fuel and avoiding generation of smoke from stored fuel in tank. This also enables smoother downward flow of biomass fuel.

The air distribution assembly 104 further includes one or more exhaust pipes 22A (in this case, two exhaust pipes are shown). In an embodiment, each pipe 22A may include an air exhaust butterfly valve 22 to control the release of excess air volume and control air velocity from the air jacket cylinder 9B that is supplied to the primary combustion furnace 6. The butterfly valve 22—or any valve—however, is optional. As previously noted, one or more dampers may be used to control air distribution into the assembly.

As previously noted, a fuel holding device in the form of a rotating furnace 26 is provided as part of the combustion furnace assembly 102. Air is supplied via nozzles 25 to the middle of the combustion furnace assembly directly on the biomass fuel on the middle of the rotating furnace 26. The rotating furnace 26 receives gravity fed biomass fuel from the biomass fuel tank assembly 110 and holds the biomass fuel for burning. The rotating furnace 26 is positioned below the combustion furnace assembly. The rotating furnace 26 is supported by supporting bars or arms 15 with hub and stabilizing rollers 29 to maintain its balance and weight distribution. In an embodiment, the rotating furnace 26 has a thickness of approximately ¾ and is made of a metal plate supported by arms 15 to avoid heat transfer straight to the shaft and bearing. The stabilizing rollers 29 act as support underneath of the rotating furnace 26 to stabilize and maintain rotation horizontally, to avoid any stress to the bearing if the rotating furnace 26 rotates and becomes unstable during rotation. In an embodiment, the diameter or dimension of the rotating furnace is approximately 33 inches and it has additional weight of the biomass fuel on it. Accordingly, the arms 15 and rollers 29 aid in stabilizing the rotation of the furnace 26 during use.

As shown in FIGS. 5 and 6, for example, in accordance with an embodiment, the rotating furnace 26 includes a support surface 26A. The support surface 26A holds and positions biomass fuel for burning in the combustion furnaces. The support surface 26A is positioned in a horizontal plane. In an embodiment, the support surface is provided on a circular plate.

In an embodiment, the support surface 26A (or circular plate) has a diameter D5 (see FIG. 6). In an embodiment, the diameter D5 is within a range of approximately 23 inches to approximately 24 inches. Of course, it should be understood that such dimensions are exemplary only and not intended to be limiting with regards to this disclosure. That is, the support surface may have a length and/or a width instead of a diameter. Further, although shown in the drawings and noted herethroughout, the use of a support surface on a circular plate is not intended to be limiting. The support surface 26A may be provided on a plate, grate, or similar device, and may be of any shape or dimension (e.g., square, rectangular, oblong, round, etc.), and thus is not limited to the depiction in the illustrated embodiment.

In an embodiment, the support surface 26A is configured for substantially continuous or continuous rotation. To rotate the rotating furnace 26, the drive and shaft assembly 108 is provided in the biomass stove 100. FIG. 7 illustrates in greater detail parts of the drive and shaft assembly 108 which includes mounting the circular plate on a vertical shaft that is configured to be driven by a motor 31 about a vertical axis A. More specifically, the drive and shaft assembly 108 has a main shaft assembly 32, a bearing assembly 30, a driven sprocket 19, a drive chain 34, a drive sprocket 33, and a main drive gear motor 31. This drive and shaft assembly 108 rotates the rotating furnace 26 and ash removal assembly 106. One gear motor 31 transmits power through the drive sprocket 33 to the driven sprocket 19 with drive chain 34 to rotate the main shaft assembly 32. The bearings in the bearing assembly 30 are for holding the main shaft assembly 32, rotating furnace 26, and a primary ash scraper 28 and a secondary ash scraper 35 of the ash removal assembly 106, each of which are described below.

In an embodiment, a support surface/circular plate 26A has at least one curved vane 22 thereon to assist in circulating biomass fuel against the wall of the fuel tank and moves the biomass fuel to the center of the combustion furnace by centripetal force during rotation of the furnace 26. In one embodiment, the support surface/circular plate 26A has a number of curved vanes 27 thereon for circulating biomass fuel. Each vane is defined as a curved object or raised wall that is rotated about the vertical axis A and causes the biomass fuel to move or be redirected as the circular plate and its surface 26A rotates (e.g., towards the center, towards the primary combustion furnace). FIG. 6 illustrates an example of using four curved vanes positioned along the support surface 26A of the circular plate.

Biomass fuel is gravity fed in a generally vertical direction onto the horizontally positioned support surface 26A of the rotating furnace 26. During rotation, the rotating furnace 26 and the curved vanes 27 create horizontal movement by centripetal force which moves the fed biomass fuel (in a substantially uniform manner) to or towards a center of the support surface 26A and thus a center of the combustion furnace assembly 102. Simultaneously, stored biomass fuel in the fuel tank continues to slowly slide downwardly, in a vertical direction, via gravity to fill any gap created by the rotating furnace 26 as the biomass fuel moves into or towards the center of rotating furnace 26.

The support surface 26A of the rotating furnace 26 also has a plurality of openings 26B therein for discharging ash from burned biomass fuel below the circular plate. In some cases, the support surface 26A may be referred to as a grate. In an embodiment, the rotating furnace 26 has openings 26B to discharge ash to a grate(s) of the ash removal assembly 106 that is positioned below the rotating furnace 26. The positioning of the openings 26B on the support surface 26A may be customized such that they are provided within an inner area having diameter that substantially matches a diameter of the secondary combustion furnace (e.g., a diameter of the inner cylinder 7A) so that ash may be discharged below to make room for introducing new fuel by the rotating furnace 26.

Accordingly, the combustion furnace assembly 102 is configured, e.g., via rotating furnace 26, to move biomass fuel horizontally by centripetal force and vertically from tank via gravity feed (as the fuel is moved towards the center and burned) downward to continue feeding fuel around the center of the primary combustion furnace 6 by rotating furnace 26 with curved vanes 27. The rotating furnace 26 is designed for substantially continuous or continuous rotation, feeding, and firing of biomass fuel, without interruption.

The rotating furnace 26 also is part of the ash removal assembly 106, since its openings discharge ash below the support surface 26A of the circular plate. The ash removal assembly 106 aids in controlling the incoming fuel and discharging ash ratio for efficient combustion. The assembly 106 is constructed to discharge ash efficiently out of the combustion furnace assembly 102 so that little to no ash accumulates on the rotating furnace 26 (so that new biomass fuel may be burned). The ash removal assembly 106 is positioned below the combustion furnace assembly 102 for receiving ash from burned biomass fuel being discharged from the fuel holding device/rotating furnace 26, and distributing the received ash to an ash pan 36 positioned below the ash removal assembly 106.

The ash removal assembly 106 further includes an adjustable ash grate 16 and a fixed ash grate 17, each placed below the rotating furnace 26, as shown in FIG. 5. The fixed ash grate 17 is positioned below the adjustable ash grate 16 along the vertical axis A. In an embodiment, the fixed ash grate 17 may be positioned parallel to the adjustable ash grate 16. The grates 16 and 17 are provided within an ash holding tank 18 (shown in FIGS. 1 and 2), designed to contain discharged ash before it is output to the ash pan 36. The ash holding tank 18 may be circular or round in shape. In an embodiment, shown in FIG. 7, the grates 16 and 17 are mounted relative to the shaft 32 that rotates the rotating furnace 26. For example, the grates 16 and 17 may be positioned above the bearing assembly 30 and below the supporting arms of the rotating furnace 26. However, the grates 16 and 17 do not rotate with the shaft 32. Rather, the grates 16 and 17 are placed in position around the shaft 32 and remain stationary relative to the rotating shaft 32. More specifically, the fixed ash grate 17 remains fixed in its position. The adjustable ash grate 16, however, may be rotated manually relative to the shaft and fixed ash grate 17 as needed. Generally, it remains stationary, but is rotatable relative to the fixed ash grate 17.

Each grate 16 and 17 includes multiple openings therein to allow ash to be discharged therethrough. In an embodiment, the adjustable ash grate 16 is circular in shape. In an embodiment, the fixed ash grate 17 is circular in shape. In one embodiment, both grates 16 and 17 are substantially circular. The adjustable ash grate 16 has a diameter D6 (see FIG. 6) in accordance with an embodiment. In an embodiment, the diameter D6 is within a range of approximately 11.5 inches to approximately 12 inches. The fixed ash grate 17 has a diameter D7 in accordance with an embodiment. In an embodiment, the diameter D7 is within a range of approximately 11.75 inches to approximately 12.25 inches. In one embodiment, the diameter D6 and diameter D7 are substantially equal. In an embodiment, the grates 16 and 17 have diameters D6 and D7 that are both less than the diameter D5 of the circular plate. In an embodiment, at least one of the grates 16 and 17 has a diameter D6 and/or D7 that are both less than the diameter D5. Of course, it should be understood that such dimensions are exemplary only and not intended to be limiting with regards to this disclosure. That is, the grates 16 and 17 are not limited to the circular shape illustrated in the Figures. For example, either or both of the ash grates 16 and 17 may instead be of another shape, and/or include dimensions such as a length and/or a width. Furthermore, the grates 16 and 17 themselves do not need to be similar in shape. For example, the adjustable ash grate 16 may be formed of one shape while the fixed ash grate 17 may be formed of another, different shape.

Adjustment of the adjustable ash grate 16 relative to the fixed ash grate 17 moves the respective openings into and out of alignment such that, upon substantial alignment of the openings, the discharged ash from burned biomass fuel is output (e.g., to an ash pan 36). In an embodiment, the rotating furnace 26 has openings 26B in its support surface 26A of the circular plate that are designed and/or customized to discharge ash to adjustable ash grate with openings 16 that is positioned below the rotating furnace 26. In accordance with an embodiment, the openings of the rotating furnace 26, the adjustable ash grate 16, and the fixed ash grate 17 has the same or substantially the same pattern and/or dimension of openings, so that a uniform volume of ash may be discharged. In an embodiment, the adjustable ash grate 16 may be rotated manually to align its openings with the openings of fixed ash grate 17. The discharged ash volume from the ash removal assembly 106 may depend on a percentage of ash generation by different biomass fuels.

The ash removal assembly 106 further includes a primary ash scraper 28 and a secondary ash scraper 35, each configured to move ash adjacent thereto. In an embodiment, the primary ash scraper 28 is positioned above the grates 16 and 17, while the secondary ash scraper 35 is positioned below the grates 16 and 17. In one embodiment, the primary ash scraper 28 is positioned within the ash holding tank 18 (see FIG. 2), while the secondary ash scraper 35 is positioned below the ash holding tank 18, adjacent to the ash pan 36.

In an embodiment, either or both the primary ash scraper 28 and the secondary ash scraper 35 are mounted to the shaft 32 and configured for rotation therewith. In the illustrated embodiment, the primary ash scraper 28 is fixed to the shaft 32, and the secondary ash scraper 35 is arranged to rotate about the vertical axis A via motor 31. Each scraper 28 and 35 includes legs extending perpendicularly from a central mounting portion in a horizontal direction. The primary ash scraper 28 has a length L (see FIG. 6). In an embodiment, the length L is within a range of approximately 10.5 inches to approximately 11 inches. The secondary ash scraper 35 has a length L2. In an embodiment, the length L2 is within a range of approximately 16 inches to approximately 17 inches. Of course, it should be understood that such dimensions are exemplary only and not intended to be limiting with regards to this disclosure. In an embodiment, the length L2 of the secondary ash scraper 35 is greater than the length L of the primary ash scraper 28. In one embodiment, the length L of the primary ash scraper 28 is substantially equal to the diameter D6 of the adjustable ash grate 16. In another embodiment, the length L of the primary ash scraper 28 is greater than the diameter D6. In yet another embodiment, the length L of the primary ash scraper 28 is substantially equal to both diameters D6 and D7 of the grates 16 and 17. In one embodiment, the length L2 of the secondary ash scraper 35 is greater than the diameters D6 and D7 of the grates 16 and 17. In another embodiment, the length L2 is less that the diameter D5 (or dimension) of the support surface/circular plate 26A.

In operation, ash drops from the rotating furnace 26 as fuel is burned and accumulates on top of the adjustable ash grate 16. One function of the primary ash scraper 28 is to rotate with rotating furnace 26 (via rotating of shaft 32) and remove discharged ash through the openings of the grates 16 and 17. The primary ash scraper 28 is configured to scrape and move accumulated dropped ash through the openings of the adjustable ash grate 16 as it rotates. In an embodiment, the primary ash scraper 28 may be positioned a distance (e.g., a couple of inches) above the adjustable ash grate 16 such that a certain level of ash may accumulate on top of the adjustable ash grate 16 in order to seal smoke or gas escaping from the ash holding tank 18 assembly to atmosphere. In one embodiment, the primary ash scraper 28 rotates continuously with rotating furnace 26.

The ash that accumulated on top of adjustable ash grate 16 is discharged to the fixed ash grate 17 via the primary scraper 28. The fixed ash grate 17 may be positioned with small gap relative to the adjustable ash grate 16 so that the grate 17 holds some ash that acts to create a secondary seal for smoke or gas escaping from the ash holding tank 18 assembly to atmosphere.

Ash discharges through the holes of the fixed ash grate 17 to the ash pan 36. The secondary ash scraper 35 rotates to flatten and spread accumulated ash on top of the ash pan 36 to make the ash holding time longer for the ash pan 36.

FIGS. 8 and 9 illustrate an example embodiment of the biomass fuel tank assembly 110 used in the biomass fuel stove 100. The tank assembly 110 is designed to be a gravity-feeding fuel holding tank that allows for a vertically metered feed of the biomass for burning as the fuel is needed. The tank assembly 110 surrounds the air jacket 9B of the combustion furnace assembly 102 and is secured to the frame assembly 20. Biomass fuel is held between walls of the outer cylinder 7C and the fuel tank (i.e., an outer wall of the air jacket and an inner wall of the fuel tank). Positioned at a bottom of the tank assembly 110 are the rotating furnace 26 and ash holding tank 18 (see also FIGS. 1 and 2).

In an embodiment, the tank assembly 110 is a substantially cylindrical tank formed from three segments that include a tank cone segment 12, a tank cylindrical segment 13 and a tank cylindrical bottom segment 14, noted in FIG. 9. The tank cone segment 12 is designed for holding a supply of biomass fuel. The tank cylindrical segment 13 is designed for inducing movement (e.g., sliding down) of biomass fuel smoothly by gravity in order to maintain fuel density inside the tank and avoid compaction effect of the biomass fuel. The cylindrical bottom segment 14 has a similar function as the tank cylindrical segment 13. A selvedge portion (shown in FIG. 2) may be provided to extend from the this portion of the tank at a position above the rotating furnace 26 in order to block biomass fuel from getting into a gap between the rotating furnace 26 and the cylindrical bottom segment 14. This selvedge portion further prevents accumulation of tar and ash in between rotating furnace 26 and bottom cover of cylindrical bottom segment 14.

Flue gas, resulting from the burning and combustion of biomass fuel in at least the primary combustion furnace 6 of the combustion furnace assembly 102, is directed from the biomass stove 100 via a flue gas pipe assembly 112, shown in FIG. 10. The pipe assembly 112 includes a perforated plate 37 that is connected to the combustion furnaces 6 and 7 (i.e., a plate with holes or openings therein). As shown in FIG. 2, for example, the perforated plate 37 is sized to connect with the outer cylinder 7C of the combustion assembly 102. In one embodiment, the perforated plate 37 is circular. The perforated plate is not required, however, in this case, it is provided as a connector to an output flue gas duct 2 for directing flue gas away from the stove 100 and into a curing barn furnace (or other enclosed space or room), noted in FIG. 12. The output flue gas duct 2 may include any number of connected segments and may include a number of bends or turns or straight portions depending on an environment, room, or space the stove 100 is positioned in. In this illustrated embodiment, connected to or around the perforated plate 37 is an elbow portion of output flue gas duct 2. The elbow portion may include secondary air holes 3. These secondary air holes 3 assist in allowing air to flow therein such that the flame continues to burn. The elbow portion also includes a flame inspection door 4 that is hingedly mounted to its outer wall. A door opener 5 is provided on the door 4 so that an operator may open the door 4. The door 4 allows an operator to ignite the biomass fuel on startup in the combustion furnace assembly 102 (e.g., by placing ignited paper into the primary combustion furnace 6). Further, the door 4 may be opened as needed to check on and ensure a desired flame is present. Furthermore, the door 4 may be used to feed biomass fuel directly into the primary combustion furnace 6 during a power interruption (so that the stove can be operated continuously and/or without substantial interruption).

In an embodiment, a perforated plate 37 (see FIG. 4) sits on top of the primary combustion furnace 6 and secondary combustion furnace 7 to stop flying ash from carrying over to the flue gas duct 2. The size or diameter of the holes or openings in the perforated plate 37 may have a diameter or dimension of ⅛ inch, ¼ inch, or ⅜ inch, as examples. The perforated plate 37 may be formed with different patterns of openings and/or with different diameter of holes depending on a type of biomass fuel being utilized, since different types of fuel generate different size and weight of ash from one to the other. For example, biomass fuel in the form of rice husks generates ash about 25% of the rice husk volume. However, other types of biomass fuel generate ash about 0.5% to 4% of their volume. Accordingly, providing an ash separator 1 in the flue gas duct 2 may also be desirable. As shown in FIG. 10, for example, an optional ash separator 1 may be provided between portions of the flue gas duct 2. The optional ash separator 1 collects fly ash pulled by convection along the flue gas duct 2. Such ash may reduce the velocity of the flue gas duct. Ash or particles that are heavier than heated air may pass through the plate, for example.

Accordingly, this disclosure provides a multiple biomass fuel or agricultural waste fired stove wherein fuel is supported by a rotating furnace 26. The rotating furnace 26 is designed for substantially continuous or continuous feeding and firing of biomass fuel without any interruptions. The rotating furnace 26 forms a means to support the burning multiple biomass fuel or agricultural waste and allows continuous feeding via gravity of biomass fuel towards or to the center of the primary combustion furnace 6. The biomass stove 100 simply requires refilling of the fuel in the tank and remove collected ash in ash pan 36. Combustion air is supplied from the fan 10 and drawn down through the air jacket cylinder 9 and air nozzles 25 to the multiple biomass fuel or agricultural waste, to aid combustion. Ash is removed without interrupting stove operation, and moved with single driver.

Further, in one embodiment, the biomass stove 100 further includes a controller and/or control panel associated therewith. The control panel may include a display or output device for displaying readings, such as a temperature reading, feed rate, discharge rate, etc. associated with the biomass stove 100. In an embodiment, the controller or control panel includes an automatic temperature controller that allows for controlling a temperature of the barn or enclosure. The controller may include a sensor, thermostat, or the like, for reading a temperature of the barn. For example, the controller may be set such that when it reads or determines via a reading that the barn has reached or exceeded a desired or required temperature, operation of the stove 100 is stopped, or at least temporarily halted, by the controller. If or when a temperature reading of the bar drops, the controller may signal for, or automatically start, operation of the stove 100.

The controller and/or control panel of the biomass stove 100 may further include one or more timers to control a feeding rate of the biomass fuel and an ash discharge rate.

The controller and/or control panel associated with the biomass stove 100 may further include a switch or selection for an operator to select an automatic or “auto” mode and a manual mode for driving the motor and/or fan. In manual mode, for example, an operator may operate and control the barn temperature by manually turning off the gear motor and/or fan (e.g., at times, simultaneously) when a target temperature is reached (as seen via the display of the control panel, for example). If or when the temperature reading of the barn drops to or near certain temperature, the gear motor and/or fan (or both) may be turned on manually by the operator (e.g., via switches). Other parts may also be manually controlled (e.g., opening of the damper or rate of rotation). In auto mode, the controller may be configured to communicate with the motor, fan, and/or other mechanical/electro-mechanical parts to alter operation in a similar manner.

In an embodiment, one or more alerts or alarms may be associated with the biomass stove 100. For example, an audio or visual alert (e.g., sounds, lights) may be associated with the biomass stove 100 to alert an operator, for example, of one or more functions, faults, or readings detected by the controller.

Some benefits of the disclosed biomass stove 100 include, but are not limited to, financial advantages, environmental benefits, and sustainability. The disclosed stove 100 has the ability to utilize biomass materials as its source of fuel for curing tobacco instead of using other traditional fuels (such as wood). Costs for curing tobacco are reduced, since there is a reduction and savings in fuel costs, as well as a reduction in emission of pollutant gases such as greenhouse gases (GHG). Additionally, the curing quality of tobacco is improved when using the disclosed biomass stove 100 since the stove 100 allows for a more precise control of temperature for each curing stage. Further, using biomass as fuel instead of firewood reduces deforestation (due to cutting of trees) as well as increased efforts and costs for reforestatation.

It should be noted that although this disclosure provides advantages for using biomass fuel over other traditional fuels, such as firewood, the stove 100 is not limited to such. That is, fuel such as firewood may be burned in the stove 100, alone or along with biomass fuel. For example, should a power interruption occur, e.g., should a flame diminish, firewood may be feed through the door 4 and into the primary combustion furnace 6 to continue operation and burning.

The charts shown in FIG. 14 illustrate results of fuel consumption between firewood versus rice husk in curing FCV (flue cured Virginia) tobacco measured during a test run implementing the disclosed stove 100. In general, as shown, rice husk consumed more kilos compared to wood, but the total cost is lesser. Accordingly, the test run illustrates that any efficiency difference may depend on biomass fuel and wood kilo cost in a location that the stove 100 is implemented. For example, in some countries, e.g., the Philippines, burning biomass fuel or rice husk in stove 100 is much more cost efficient as compared to wood (e.g., rice husk is 42% more cost efficient than firewood).

While the principles of the disclosure have been made clear in the illustrative embodiments set forth above, it will be apparent to those skilled in the art that various modifications may be made to the structure, arrangement, proportion, elements, materials, and components used in the practice of the disclosure. For example, as noted throughout, the shapes as shown in the illustrated Figures, and reference to any dimension, is not intended to be limited to those depicted or described. The round or circular shape of the furnaces, grates, plates, support surface, and the like are exemplary, and such devices may comprise other shapes. Further, the dimensions (e.g., diameters) noted are not intended to be limiting.

It will thus be seen that the features of this disclosure have been fully and effectively accomplished. It will be realized, however, that the foregoing preferred specific embodiments have been shown and described for the purpose of illustrating the functional and structural principles of this disclosure and are subject to change without departure from such principles. Therefore, this disclosure includes all modifications encompassed within the spirit and scope of the following claims. 

What is claimed is:
 1. A biomass stove for burning biomass fuel using a combustion furnace comprising: a fuel holding tank for feeding biomass fuel to the combustion furnace; a rotating furnace positioned below the combustion furnace for receiving the biomass fuel from the fuel holding tank; and a motor, wherein the rotating furnace includes a support surface configured for rotation by the motor, the support surface constructed to hold and position biomass fuel for burning in the combustion furnace.
 2. The stove according to claim 1, wherein the support surface is provided on a circular plate, the support surface being positioned in a horizontal plane, and wherein the circular plate is connected to a vertical shaft that is configured to be driven by the motor about a vertical axis.
 3. The stove according to claim 1, wherein the fuel holding tank is a gravity-feeding fuel holding tank configured to feed biomass fuel via gravity in a generally vertical direction onto the support surface of the rotating furnace.
 4. The stove according to claim 3, wherein the support surface comprises at least one curved vane thereon to assist in circulating the gravity fed biomass fuel during rotation of the rotating furnace.
 5. The stove according to claim 4, further comprising plurality of curved vanes thereon.
 6. The stove according to claim 1, wherein the support surface comprises a plurality of openings for discharging ash from burned biomass fuel below the support surface, and wherein the stove further comprises an ash removal assembly for receiving ash from burned biomass fuel being discharged from the rotating furnace.
 7. A biomass stove for burning biomass fuel using a combustion furnace comprising: a fuel holding tank for feeding biomass fuel to the combustion furnace; a fuel holding device for receiving the biomass fuel from the fuel holding tank and positioning biomass fuel for burning in the combustion furnace; and an ash removal assembly positioned below the combustion furnace for receiving ash from burned biomass fuel being discharged from the fuel holding device and distributing the received ash to an ash pan positioned below the ash removal assembly; the ash removal assembly comprising an adjustable ash grate and a fixed ash grate, the fixed ash grate positioned below the adjustable ash grate, and each grate comprising a plurality of openings therein, wherein adjustment of the adjustable ash grate relative to the fixed ash grate moves its openings into and out of alignment with openings on the fixed ash grate such that, upon substantial alignment of the openings, ash from burned biomass fuel is output to the ash pan.
 8. The stove according to claim 7, wherein the adjustable ash grate is arranged to rotate about a vertical axis.
 9. The stove according to claim 8, further comprising a primary ash scraper and a secondary ash scraper each configured to move ash adjacent thereto, wherein the primary ash scraper is positioned above the grates, and wherein the secondary ash scraper is positioned below the grates.
 10. The stove according to claim 9, wherein the secondary ash scraper is arranged to rotate about the vertical axis.
 11. A biomass stove for burning biomass fuel using a combustion furnace assembly comprising: the combustion furnace assembly comprising: a primary combustion furnace for burning biomass fuel; a secondary combustion furnace surrounding the primary combustion furnace, the secondary combustion furnace having an inner wall spaced from an outer wall of the primary combustion furnace; a water jacket surrounding the secondary combustion furnace; an air jacket further surrounding the water jacket, and a fuel holding device for receiving the biomass fuel and positioning biomass fuel for burning in the primary combustion furnace.
 12. The stove according to claim 11, further comprising a fuel holding tank for feeding biomass fuel to the combustion furnace, wherein the fuel holding tank surrounds the air jacket and the biomass fuel is held and fed between an outer wall of the air jacket and an inner wall of the fuel holding tank.
 13. The stove according to claim 12, wherein the fuel holding tank is a gravity-feeding fuel holding tank configured to feed biomass fuel via gravity in a generally vertical direction onto the fuel holding device.
 14. The stove according to claim 11, wherein the fuel holding device comprises a rotating furnace positioned below the primary combustion furnace and a motor, wherein the rotating furnace includes a support surface configured for rotation by the motor, the support surface constructed to hold and position biomass fuel for burning in the primary combustion furnace.
 15. The stove according to claim 14, wherein the support surface is positioned in a horizontal plane, and wherein the support surface is connected to a vertical shaft that is configured to be driven by the motor about a vertical axis.
 16. The stove according to claim 15, wherein the support surface comprises at least one curved vane thereon to assist in circulating the fed biomass fuel during rotation of the rotating furnace.
 17. The stove according to claim 16, further comprising plurality of curved vanes thereon.
 18. The stove according to claim 11, wherein the fuel holding device comprises a plurality of openings for discharging ash from burned biomass fuel therebelow, and wherein the stove further comprises an ash removal assembly positioned below the combustion furnace assembly for receiving discharged ash from burned biomass fuel and distributing the received ash to an ash pan positioned below the ash removal assembly.
 19. The stove according to claim 18, wherein the ash removal assembly comprises an adjustable ash grate and a fixed ash grate, the fixed ash grate positioned below the adjustable ash grate, and each grate comprising a plurality of openings therein, wherein adjustment of the adjustable ash grate relative to the fixed ash grate moves its openings into and out of alignment with openings on the fixed ash grate such that, upon substantial alignment of the openings, ash from burned biomass fuel is output to the ash pan. 